In situ transmission electron microscopy study of dielectric breakdown of surface oxides during electric field-assisted sintering of nickel nanoparticles

Local Current-Activated Growth of Individual Nanostructures with High Aspect Ratios

“…Initially, no significant current was observed due to the presence of mostly insulating surface oxide layers that cover the metallic nanoparticles. [16,17] During the holding interval with a constant bias of +4.0 V the observed current abruptly increases to approximately 60 μA. This observation coincides with some particle rearrangement (see Supplementary online video clip) and is consistent with previously observed dielectric breakdown behavior of surface oxide films covering individual nanoparticles.…”

“…This observation coincides with some particle rearrangement (see Supplementary online video clip) and is consistent with previously observed dielectric breakdown behavior of surface oxide films covering individual nanoparticles. [16,18] The experimentally observed current continued to increase linearly to approximately 70 μA albeit at a reduced rate. Once the particle agglomerate became conducting, gradually increasing currents during the holding intervals were observed for each bias setting.…”

Consolidation of Partially StabilizedZrO2in the Presence of a Noncontacting Electric Field

“…Francis and co-workers postulated that the applied electric field creates a high concentration of defects within the material that can increase both mass transport and electrical conductivity. [19] This description is consistent with dielectric breakdown phenomena that ultimately lead to local leakage currents [20] and thus, current assisted densification [11,30,31].…”

“…[15] Subsequently, Bonifacio et al have shown that dielectric breakdown of insulating surface oxide layers can cause a retardation for current-assisted consolidation, and was recognized as a dominant mechanism for previously observed surface cleaning effects. [16,20] Unlike for the two-particle configuration, consolidation of larger particle agglomerates also includes information about pore evolution that is essential to be considered for sintering studies.…”

“…It is still under debate, however, whether the applied electric field, the resulting current through the sample, or both are responsible for the accelerated sintering. [11] While the current flow throughout the sample could enhance densification through suggested mechanisms such as electromigration, [12,13] Joule heating, [14,15] and self-cleaning [16,17] at grain boundaries, it is proposed that the electric field could enhance sintering by nucleation of point defects, [18,19] dielectric breakdown of insulating surface layers, [20,21] and interactions with space charge layers [18,22].…”